This invention relates to a system for treating solid particulate material. More particularly, the system of this invention proves for the ultimate mixing of an adherable substance with solid particulate material on a continuous basis. This invention is particularly suited to cereal grain tempering processes involving the admixture of controlled amounts of water to the grain while a grain is being conveyed from one storage bin to another.
In traditional milling operations grain was washed clean before milling and the cleaning water discarded. This was typically accomplished by grain washing apparatus that immersed the grain in water and then spun the grain to centrifuge the water off. Any material adhering to the hull of the grain was carried away by the water. Inherently, the immersion step resulted in water adhering to the grain surface and absorbed into the grain, thus raising the grain mositure level. The wet processes are now all but abandoned due to the difficulties in processing the resultant streams of polluted water formed as a by-product.
Millers have now converted to dry scouring processes to comply with water pollution regulations. Dry scourers remove adherent impurities but do not wet the grain. Consequently, subsequent processing of the grain must involve water addition since milling processes are most productive when operating on tempered grain.
Because grain has been typically conveyed from one storage to another with screw conveyors, millers combined material and water in a screw conveyor to provide for water addition. Such systems required the use of long screw conveyors to enable the water added in the wetting screw to penetrate the grain, otherwise the added water would run off and puddle when the grain was subsequently stored. This system allowed a maximum addition of about 3% of water to wheat, for example.
The applicant herein recognized that such screw conveyor systems did not mix the grain to ensure even wetting.
Therefore, the applicant developed a paddle mixer-conveyor system that provided a far superior alternative to wetting screw conveyor systems. The paddle mixer-conveyor utilized paddles oriented to lift the grain upward such that some kernels advance and some fall back to be mixed again. This paddle mixer-conveyor uniquely created such enormous particle-to-particle surface contact that free moisture (i.e. unpenetrated moisture) distribution among the particles was accomplished with a then-hitherto-unknown efficiency and with a much shorter conveyor length. In the case of water addition to wheat, for example, superior moisture addition could be obtained within about 18 to 20 seconds in amounts up to the adhesion water/wheat limit of about 4.5% water without subsequent water runoff.